Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (874 page)

CREATININE, URINE

   Definition

   Creatine is synthesized from amino acids in the kidney, liver, and pancreas. The creatine is then transported in the blood to other organs where it is synthesized into creatinine. In the absence of kidney disease, the urinary creatinine is excreted in rather constant amounts and represents glomerular filtration and active tubular excretion of the kidney. Because the creatinine is excreted from the body at a constant rate, there are expected values for creatinine in normal human urine. Specimen validity testing is the evaluation of the specimen to determine if it is consistent with normal human urine (creatinine values >20 mg/dL). Creatinine is made at a steady rate and is not affected by diet or by normal physical activities.

   
Normal range:
see Table 16.25.

TABLE 16–25. Normal Values for Urine Creatinine

   Use

   Urinary creatinine, in conjunction with serum creatinine, is used to calculate the creatinine clearance, a measure of renal function.

   Interpretation

Increased In

   Exercise

   Acromegaly

   Gigantism

   DM

   Infections

   Hypothyroidism